An image forming apparatus having an image reading device, which is provided above a top surface of an apparatus body, is known as an image forming apparatus of in-body discharge type. In such image forming apparatus, a cover section is provided so as to function as the top surface of the apparatus body to cover the inside of the apparatus body. Further, a support section is provided between the cover section and the image reading device so as to support and keep the image reading device at the location above the cover section.
In order to allow an operator to easily access the inside of the apparatus body, the cover section is rotatably provided on the apparatus body. When needed, the cover section rotates around a rotational shaft attached to a rear section of the apparatus body to be away from a front side of the apparatus body facing the operator, and the inside section of the apparatus body is exposed to the operator. Further, an exposure glass cover of the image reading device rotates about a rotational shaft having the same rotational axis with the rotational shaft attached to the rear section of the apparatus body. For this reason, if the operator opens the cover section while the exposure glass cover is open, the exposure glass cover may be widely opened due to gravity such that the exposure glass cover may hit an object located near the apparatus.
Japanese Patent No. 3644376 describes an image forming apparatus having a lock mechanism, which prevents the exposure glass cover and the cover section to be open at the same time.
In addition to making the cover section rotatable to expose the inside of the apparatus body, the image reading device may be caused to slide with respect to the cover section, for example, as described in Japanese Patent No. 3176411. This further improves operability for the operator especially when a printed sheet is discharged onto an output sheet tray provided on the cover section, which is located below the image reading device. However, the image forming apparatus described in Japanese Patent No. 3176411 is not provided with a lock mechanism, which prevents the cover section from opening when the exposure glass cover is open. Even with assumption that the image forming apparatus having the lock mechanism as described in Japanese Patent No. 3644376 is implemented to have the image reading device slidable, the position of the image reading device relative to the apparatus body changes as the image reading device slides. Accordingly, the lock mechanism of Japanese Patent No. 3644376 may not be able to prevent opening of the cover section throughout the entire slidable range of the image reading device.
Further, the image forming apparatus may be provided with a book document, which is thick. In such case, the exposure glass cover may not be in close contact with the exposure glass even when it is closed. When the cover section is open, the exposure glass cover may widely open as described above. In view of this problem, a lock mechanism should be able to prevent opening of the cover section when the exposure glass cover is not in close contact with the exposure glass.
Further, when the image reading device is made slidable as described in Japanese Patent No. 3176411, the image reading device may slide due to gravity with opening of the cover section or the exposure glass cover. This may further cause the image reading device to hit an object located near the apparatus or hit the operator. The image forming apparatus of Japanese Patent No. 3176411, however, is not provided with a lock mechanism that prevents sliding of the image reading device.